Most of Sigils "Do something on next hit after weapon swap" work 1 time after you actually equip your weapon from inventory. They dont proc off Attunement Swap, so pretty much useless.

Heavily tested Sigil[s] of Superior Earth with 90% critchance build for consistency:
It has hidden inner cooldown, something close to 0.2 seconds. It never ever procced twice from single cast while spamming Scepter Earth 1. It did reliably proc two times during Scepter Air 1 channel (at the start and at the end).
I suspect all "Proc on crit" Sigils work similarly. Thus, due to inner cooldown it is a bad idea to equip two on-crit proc Sigils at the same time. They will conflict with each other, even if tooltip says they have no cooldown (they still have it hidden 0.2s).

Also noticed a weird bug - Sigil[s] of Superior Earth never ever procced while being slotted into Scepter. It worked fine if slotted into dagger (both mainhand and offhand).
Therefore I recommend slotting all these randomly proccing Sigils into Daggers (or Foci/Staves if you prefer). Or test it to be sure.

TLDR CONCLUSION:

Sigils with cooldowns share cooldowns (i.e. Sigil of Superior Geomancy and Superior Sigil of Air).
Sigils with procs but without cooldowns (i.e. Sigil of Superior Strength) effectively have 0 seconds cooldown timer. So they do not proc if they are paired with cooldown-based proc Sigil and the latter's "Sigil cooldown" is still ticking.
Sigils that "proc" but have no cooldown listed (i.e. Sigil[s] of Superior Earth ) have hidden internal cooldown of ~0.2 seconds. So it is suboptimal to equip any two of those as well.

Thus, it is suboptimal to use cooldown-based proc Sigil - whether it is a crit-proc or swap-proc - with any other proc Sigil.

Sigil of Intelligence DOES work, but gets used up by the minor traits that so some small aoe damage upon attunement switching (fire, air, earth, etc.) which sucks because you'll pretty much always have one of those traits.

I would like to ask if you tested with 2 crit proc sigils such as Sigil of Superior Strength on dual weapons. Is it possible to gain 2 might stacks with a single crit or would 1 overwrite the other and only gain 1 might stack

When I was testing Sigil of Superior Energy even passive sigils like force and agony were interfering with it. I was only able to make it work running it in both sigil slots simultaneously.

I really hope anet spends more time fixing broken functionality, and maybe clarifying what is intended. I know everyone is discussing class balance, but things like runes and sigils not functioning properly has a significant impact on what builds work.

Sigil of superior leeching does infact work, just not on the golems. It will only activate if you are missing health. Go test it on the Class training dummies in the heart of the mists for proof.

Just tested, using d/d and got no HP after swap, only at water, but from water bonuses...
But had sigil of battle (one that adds might). Without sigil of battle, got heal but only once, I guess it has long recharge.

The sigils that are based on weapon attacks don't work, but the ones that work on just aoe do. I think the reason is because it's Weapon based. You are correct, none of the sigils that proc based on attack after weapons swap work. This makes sense as we are not actually changing the weapons themselves.

Ok I was running Hydromancy and Geomancy but I guess only Hydromancy is working. Did you try with say, dual Hydromancy to see what happened there? Or is it better to run a simple 5% crit or damage on one hand and an on-switch proc on the other?

Ok I was running Hydromancy and Geomancy but I guess only Hydromancy is working. Did you try with say, dual Hydromancy to see what happened there? Or is it better to run a simple 5% crit or damage on one hand and an on-switch proc on the other?

The cooldowns on sigils put everything on cooldown so stacking 2 active sigils is a complete waste.

Resurrecting my old thread since it is still useful and the questions I mention are still being asked occasionaly.

Also did some more testing.

Most of Sigils "Do something on next hit after weapon swap" work 1 time after you actually equip your weapon from inventory. They dont proc off Attunement Swap, so pretty much useless.

Heavily tested Sigil[s] of Superior Earth with 90% critchance build for consistency:
It has hidden inner cooldown, something close to 0.2 seconds. It never ever procced twice during single cast while spamming Scepter Earth 1. It did reliably proc two times during Scepter Air 1 channel (at the start and at the end).
I suspect all "Proc on crit" Sigils work similarly. Thus, due to inner cooldown it is a bad idea to equip two on-crit proc Sigils at the same time. They will conflict with each other, even if tooltip says they have no cooldown (they still have it hidden 0.2s).

Also noticed a weird bug - Sigil[s] of Superior Earth never ever procced while being slotted into Scepter. It worked fine if slotted into dagger (mainhand or offhand).
Therefore I recommend slotting all these randomly proccing Sigils into Daggers (or Foci/Staves if you prefer). Or test it to be sure.